Childhood aggression and delinquency exact enormous social, economic, and psychological costs and are predictive of later antisocial behavior. Recent models of the formation and maintenance of externalizing problems include hypotheses involving emotion regulation; however, empirical investigations of the links between affective processes and disruptive behavior are limited. This study examines the regulation of anger in early childhood, its relation to child and parent factors in infancy and toddlerhood, and its role in the development of conduct problems in a community sample of 310 low-SES boys. Difficult temperament, attachment security, and parental nurturance were assessed at ages 1.5-2 years. Boys completed frustration tasks at age 3.5. Boys' regulatory strategies and angry affect and maternal behavior relevant to self-regulation were recorded on videotape for later coding. In addition, mothers completed measures of boys' externalizing behavior at age 3.5, and mothers, secondary caregivers, and teachers rated externalizing behavior and reactive aggression at age 6. This research has implications for improving developmental models of externalizing behavior problems and for informing prevention and intervention strategies in at-risk and antisocial children.